Through flow fluid treatment apparatus

ABSTRACT

This invention relates to a through flow heat exchanger or other fluid treatment apparatus. The treatment apparatus has a battery of treatment tubes in a treatment compartment. The treatment apparatus also has an inlet and an outlet and flow control means so that fluid can normally flow through the tubes in one flow pattern. The flow control means can be changed for temporary operation to produce a different flow pattern. The volumetric flow rate through the apparatus varies but the linear flow rate through the tubes is constant. The apparatus may be incorporated in trains so that one train can be spared for maintenance leaving the other train or trains to process all the fluid.

MacKenzie [451 Apr. 2, 1974 THROUGH FLOW FLUID TREATMENT APPARATUS [75] inventor: Peter J. MacKenzie, Mount Waverley, Victoria, Australia [73] Assignee: Woodall Duckham Limited,

Melbourne, Australia 22 Filed: June 7, 1971 [21] Appl. No.: 150,559

[30] Foreign Application Priority Data 2,256,535 9/1941 Tuley 165/97 X FOREIGN PATENTS OR APPLICATIONS 802,538 6/1936 France 165/101 160,264 12/1954 Australia..... 165/101 85,124 5/1920 Switzerland 165/101 Primary Examiner-William F. ODea Assistant ExaminerWilliam C. Anderson Attorney, Agent, or Firm-William A. Knoeller [57] ABSTRACT This invention relates to a through flow heat exchanger or other fluid treatment apparatus. The treatment apparatus has a battery of treatment tubes in a treatment compartment. The treatment apparatus also has an inlet and an outlet and flow control means so that fluid can normally flow through the tubes in one flow pattern. The flow control means can be changed for temporary operation to produce a different flow pattern. The volumetric flow rate through the apparatus varies but the linear flow rate through the tubes is constant. The apparatus may be incorporated in trains so that one train can be spared for maintenance leaving the other train or trains to process all the fluid.

13 Claims, 9 Drawing Figures PATENTEI] APR 2 I974 sum 1 or 3 THROUGH FLOW FLUID TREATMENT APPARATUS The present invention relates to heat exchangers and other through flow fluid treatment apparatus for treating fluid flowing therethrough; such treatment apparatus being of the kind including: a fluid inlet, a fluid outlet, and a plurality of fluid treatment tubes connected between the fluid inlet and the fluid outlet so that fluid to be treated enters the fluid inlet and flows through the treatment tubes in a flow pattern to the fluid outlet. The invention also relates to through flow fluid treatment plant incorporating such treatment apparatus.

Although not limited thereto, the invention is applicable to alumina plants which use through flow fluid heat exchangers or trains of such heat exchangers. It is convenient to refer to this particular use of through flow fluid treatment apparatus to describe attributes of the invention.

All alumina plants do not use the same treatment processes, but it is common in some plants to use sodium aluminate liquor which contains caustic soda or sodium hydroxide as an active component for the treatment of bauxite to dissolve aluminum oxide therefrom and subsequently precipitate the oxide from the liquor in crystal form. -In the process the caustic soda component generally becomes diluted. It is desirable to recover the caustic soda for reuse but for this purpose the liquor should be concentrated.

In practice the sodium aluminate liquor is generally concentrated by removing some of the water content by evaporation. The apparatus employed for this purpose may include heat exchangers coupled together to process the sodium aluminate liquor. When the liquor passes through the heat exchangers it is heated and subsequently the heated liquor may be passed through evaporator units such as vacuum flash evaporators to take off the water and thus concentrate the liquor.

Each heat exchanger may include a plurality of treatment tubes arranged to receive a flow of liquor therethrough. A heating medium may pass around the outside of the treatment tubes to heat the liquor therein. It is convenient to use as the heating medium steam coming from the evaporator units.

During the process, scale deposits form on the inside surfaces of the treatment tubes progressively clogging them and restricting the flow of liquor therethrough. This scale is periodically removed mechanically or by passing a cleaning fluid through the treatment tubes. During cleaning the heat exchangers are not used to treat the sodium aluminate liquor.

Removal of the scale from the heat exchangers may be carried out by sparing the whole plant until the treatment tubes are cleaned, but such sparing leaves associated high cost apparatus idle.

Alternatively the heat exchangers may be specially arranged so that one at a time may be spared for cleaning purposes leaving the others in action. However this involves complicated valving arrangements to exclude each heat exchanger for cleaning. A further alternative is to arrange the heat exchangers within a plant in two or more parallel trains so that a train may be isolated for cleaning while the remaining train or trains continue to operate at reduced efficiency.

To maintain the rate of production of the plant with such arrangements operating temporarily during cleaning, the treatment tubes of the heat exchangers remaining in operation need to pass liquor at the same volumetric flow rate as when all the heat exchangers are in operation. This ncessarily requires that the liquor flowing through the treatment tubes remaining in operation must flow at an increased linear flow rate during temporary operation. For this purpose excess pumping capacity is required to build up the linear flow rate but such excess pumping capacity is costly because it is unused during normal operation.

The primary object of the present invention is to provide improved through flow fluid treatment apparatus which is capable, during temporary operation, of processing an increased volume of liquor through the treatment tubes but without necessarily requiring an increase in the associated pumping capacity.

Accordingly through flow fluid treatment apparatus according to the invention is characterised by the provision of adjustable flow control means associated with the fluid treatment tubes for controlling the flow pattern of the fluid through the treatment tubes. The flow control means is selectively adjustable to modify the flow pattern of the fluid flowing through the treatment tubes to thereby permit selected variation in the volumetric flow rate of fluid flowing through the treatment apparatus whilst the linear flow rate of the fluid flowing through the treatment tubes is maintained substantially constant.

The treatment tubes are preferably arranged in banks so that the fluid flows through the banks of treatment tubes, the bank arrangements being dependent on the adjustment of the flow control means. For example, in one arrangement the flow control means may be ad justable between a normal position and a temporary position so that in the temporary position the treatment tubes are arranged in half the number of banks compared with the normal position. This arrangement permits substantially twice the volumetric flow rate through the fluid treatment apparatus during temporary operation as compared with normal operation when the flow control means is in the normal position.

The treatment apparatus may include a vessel housing forming an enclosed vessel chamber with the fluid inlet and the fluid outlet formed as part of the vessel housing and the treatment tubes and the flow control means located in the vessel housing. It is preferred that the vessel chamber is partitioned to include a treatment compartment with the treatment tubes being located in the treatment compartment. With this arrangement the vessel housing preferably has an intake and an exhaust for receiving and exhausting treatment medium to flow through the treatment compartment and around the treatment tubes.

According to a further aspect, the invention also provides through flow fluid treatment plant including: a plurality of flui'd treatment trains connected in parallel so that in normal operation fluid to be treated by the plant flows through both of the trains. Each such train includes at least one fluid treatment apparatus according to the invention and preferably a plurality of such fluid treatment apparatus. The plant also includes isolating valve means coupled with the trains for isolating one of the trains from the fluid flow.

It will be appreciated that the treatment tubes in the treatment apparatus of an isolated train may be cleaned while the remaining train or trains continue in temporary operation passing all of the fluid flow.

In a preferred arrangement a treatment plant according to the invention includes two fluid treatment trains connected in parallel each train including a plurality of fluid treatment apparatus according to the invention. In this arrangement the treatment apparatus in each train are connected in series and in normal operation fluid flows through both trains. The isolating valve means is coupled with both trains for isolating either one of them from the fluid flow so that the fluid is then constrained to flow through the other of the trains.

It is now proposed to describe the essential and various optional features of the invention in more detail. To facilitate understanding of the invention and these features, reference is made to the accompanying drawings where the features are illustrated in preferred form. It is to be understood however, that the essential and optional features of the invention are not limited to the specific forms of these features as they are shown in the drawings.

In the drawings:

FIG. 1 is a sectional elevation of one embodiment of a through flow fluid treatment apparatus according to the invention.

FIG. 2 is an end elevation from the right hand side of FIG. 1 but with part of the flow control means omitted.

FIG. 3 is a view in the direction IIIIII of FIG. 1 showing the tube sheet at the transfer end of the treatment apparatus and showing schematically some of the treatment tube ends projecting through the tube sheet and also showing the diametric zone where the transfer baffle joins the tube sheet.

FIG. 4 is a view in the direction IV'IV of FIG. 1 showing the tube sheet at the opposite end of the treatment apparatus and also showing schematically some of the treatment tube ends as well as the diametric and two spaced cross partitions where they join that tube sheet.

FIG. 5 is an enlarged view of the upper right hand end of FIG. 1 but with part of the flow control means omitted.

FIG. 6 shows the part of the flow control means omitted from FIG. 5 and which in use is mounted in the corresponding cavity shown in FIG. 5.

FIG. 7 is a cross section of part of a control valve assembly shown in position for normal operation and shown in phantom line for temporary operation.

FIG. 8 shows a schematic view of the flow pattern through the treatment apparatus from the fluid inlet to the fluid outlet for normal operation.

FIG. 9 shows a schematic view of the flow pattern through the treatment apparatus from the fluid inlet to the fluid outlet for temporary operation.

FIG. 1 shows a preferred embodiment of through flow fluid treatment apparatus according to the invention. The particular embodiment shows the treatment apparatus in a form suitable for use as a heat exchanger. For example, the treatment apparatus shown in FIG. 1 and the remaining Figures of the drawings may be used to heat liquor flowing through the treatment tubes by means of steam used as the heating medium flowing around the treatment tubes. The invention is not limited to this use and the following description explains the invention in more general terms.

The treatment apparatus according to the invention includes a fluid inlet 11 shown in FIGS. 1 and 2 and a fluid outlet 12 shown in FIG. 2. The treatment appara tus also includes a plurality of fluid treatment tubes 14 connected between the fluid inlet 11 and the fluid outlet 12 so that fluid entering the fluid inlet 1 1 flows through the treatment tubes 14 in a flow pattern to the fluid outlet 12. In the particular arrangement shown the fluid is adapted to flow through the treatment tubes 14 back and forth along the length of the apparatus but this function is described more fully hereafter.

In accordance with the invention the treatment apparatus is characterised by the provision of adjustable flow control means 16 associated with the fluid treatment tubes 14 for controlling the flow pattern of the fluid through the treatment tubes. The flow control means 16 is selectively adjustable to modify the flow pattern of the fluid flowing through the treatment tubes 14 so as to thereby permit selected variation in the volumetric flow rate of fluid flowing through the apparatus whilst at the same time maintaining the linear flow rate of the fluid through the treatment tubes 14 substantially constant.

The treatment tubes 14 are preferably arranged in banks so that the fluid flows through the banks of treatment tubes. These bank arrangements are dependent on the adjustment of the flow control means 16. In the arrangement shown in the drawings, FIG. 8 shows that when the flow control means is adjusted for normal operation the treatment tubes 14 are arranged in four banks A, B, C and D whereas for temporary operation the treatment tubes are arranged in two banks E and F. With the arrangement of four banks the fluid is adapted to pass through the treatment tubes 14 four times along the length of the apparatus, thus being a four pass arrangement whereas for temporary operation with only two banks the apparatus is a two pass arrangement.

Thus the flow control means 16 is preferably adjustable between two positions, namely a normal position and a temporary position. It will be appreciated that other arrangements are possible where the flow control means is adjustable between a larger number of operative positions.

In addition, it will be noted that in the preferred embodiment disclosed, the treatment tubes in the temporary position are arranged in half the number of banks compared with the normal position so as to permit substantially twice the volumetric flow rate through the treatment apparatus compared with the normal position. This is a particularly suitable arrangement where the treatment apparatus are utilized in a treatment plant having two parallel trains.

However, other arrangements come within the scope of the invention and it will be appreciated, for example, that if three trains were employed in parallel it would be desirable for each treatment apparatus to be able to process a 50 percent increase in volume in temporary operation to' compensate when one of the trains was isolated and out of operation for cleaning or other maintenance purposes.

The treatment apparatus is preferably constructed so as to include a vessel housing 17 forming an enclosed vessel chamber. Both the fluid inlet and the fluid outlet 12 are preferably formed as part of the vessel housing 17 such as shown in FIGS. 1 and 2. With this arrangement the treatment tubes 14 and flow control means 16 are preferably located in the vessel housing 17.

The vessel chamber preferably incorporates a separate treatment compartment 18 with the treatment tubes 14 located in the treatment compartment 18 as shown in FIG. 1. The vessel housing 17 also preferably has an intake 19 and an exhaust 21 for the purpose of receiving and exhausting treatment medium such as steam so that the treatment medium can flow through the treatment compartment 18 and around the treatment tubes 14 in heat exchanging relationship therewith in order to heat liquor or other fluid flowing through the treatment tubes 14.

In the arrangement of FIG. 1 the vessel housing 17 is of elongated formation forming a correspondingly elongated vessel chamber. The vessel chamber is preferably divided into three compartments, namely a flow control compartment 22, the aforesaid treatment compartment 18, and a transfer compartment 23. The treatment compartment 18 is preferably located between the other two compartments 22, 23 and is preferably separated therefrom by a pair of spaced partitions or tube sheets 24, 26. The treatment compartment 18 is preferably substantially longer than either of the other two compartments 22, 23 and each treatment tube 14 extends the length of the treatment compartment 18 and opens at one end into the flow control compartment 22 and at the other end into the transfer compartment 23. This means that fluid entering one end of a treatment tube 14 from the flow control compartment 22 may flow the length of that tube through the treatment compartment and into the transfer compartment 23.

With this preferred arrangement the fluid inlet 11 and fluid outlet 12 may both be connected to the flow control compartment 22. The flow control means 16 preferably includes flow control valve means mounted for operation in the flow control compartment 22 and selectively adjustable to modify the flow pattern of the fluid as aforesaid.

The transfer compartment 23 is preferably divided into transfer chambers. For this purpose preferably at least one diametric transfer baffle 29 is provided. This has the effect of dividing the transfer compartment into two transfer chambers 27, 28.

The flow control compartment 22 is preferably divided by cell partitions into a plurality of cells. Each cell is in fluid communication with a separate group of treatment tubes 14 and one of the cells 31 is in fluid communication with the fluid inlet 11 and a separate one of the cells 32 is in fluid communication with the fluid outlet 12.

The flow control valve means is preferably so mounted in the flow control compartment 22 as to interact with the cell partitions to achieve the desired control in the flow pattern of the fluid passing through the apparatus.

FIG. 1 shows a preferred arrangement wherein the flow control valve means includes two butterfly valve assemblies 33, 34. Each butterfly valve assembly has a butterfly valve member 36 mounted for operation in the cell partitions. FIG. 7 shows that each butterfly valve member 36 is movable between two operative positions, namely a normal position shown in full line and a temporary position shown in phantom line.

FIG. 4 gives an indication of a preferred arrangement of cell partitions showing a diametric partition 37 and two spaced cross partitions 38, 39, both extending transversely of the diametric partition. Valve apertures 41 are formed in the cell partitions at the two zones of intersection between the diametric 37 and cross partitions 38, 39. The valve aperture 41 in the diametric partition 37 for one of the valve assemblies 33 is shown in FIG. 5 and the corresponding valve aperture in the cross partition is substantially the same.

FIG. 6 discloses one form of butterfly valve assembly 33 adapted to slide into the arrangement shown in FIG. 5. The butterfly valve member 36 is of complimentary shape to the butterfly valve aperture 41 provided in the diametric and cross partitions.

FIG. 6 shows a preferred form of butterfly valve including a valve spindle 43 carrying a valve plate. The valve plate may be in two parts or wings 46, 47 extending radially in opposite directions from the valve spindle 43. The valve spindle 43 is adapted for mounting in an inner 48 bearing and an outer bearing 49. The valve spindle 43 extends through the wall of the apparatus and in use is adapted for rotation in the bearings 48, 49. The outer end 51 of the valve spindle may be shaped to receive an operating tool and the valve spindle 43 is preferably rotatable through 360.

The associated valve apertures 41 in the cell partitions correspond generally in shape to the valve plate, so that when the valve plate is in line with one or other of the partitions it closes the corresponding valve aperture. Each valve aperture 41 is defined by a marginal edge portion 52 which is preferably of wedge shaped formation in cross-section. The marginal edges 53 of the valve wings 46, 47 are also preferably of wedge shaped formation in cross-section. This is shown in FIG. 7.

In use there may be a build up of scale or other deposit on the co-operating edge portions 53, 52 of the valve wings 46, 47 and valve apertures 41. The wedge shaped formation tends to minimize the binding or locking effect produced in this way.

The treatment apparatus of the drawings may function as a heat exchanger heating liquor passing through the treatment tubes 14 and using steam as the heating medium. The steam enters the intake 19 flowing around the treatment tubes 14 in the treatment compartment 18 and out of exhaust 21. Some or all of the steam may condense in this process.

In normal operation both butterfly valves 33, 34 are set so that their valve wings 46, 47 are substantially horizontal and in line with their cross partitions 38, 39. Such a normal operation position is shown schematically in FIG. 8. The transfer compartment 23 is divided by the stationary horizontal baffle 29 into two transfer chambers 27, 28. The stationary baffle 29 is shown in dotted line in FIGS. 8 and 9.

In normal operation the heat exchanger works as a four pass arrangement with four banks of treatment tubes 14. Liquor to be treated enters through the inlet 11 into the bottom right hand cell 31 of the FIG. 8. The fluid may pass through the upright diametric partition into the adjacent left hand cell 56. The treatment tubes in communication with these two cells 31, 56 constitute the first bank of tubes A.

The liquor flows along the first bank of tubes A to the transfer compartment 23 and enters the lower chamber 27 thereof. The liquor is excluded from the upper chamber 28 by the baffle 29 but can enter the second bank of treatment tubes B immediately above the first bank.

The liquor then flows along the second bank of tubes B back to the flow control compartment 22 and to the central cells thereof. These central cells are in communication through the diametric cell partition and isolated from the upper most and lowermost cells by the cross partitions 38, 39 and the in-line butterfly valve members 36. Accordingly the liquor flows along the third band of tubes C above the second bank B back to the transfer compartment 23 and in particular the upper chamber 28 thereof.

From there it returns long the top or fourth bank of tubes D back to the uppermost pair of control cells 32, 57 and out the outlet 12.

The liquor is pumped through the tubes 14 of the heat exchanger at a substantially constant linear flow rate. This rate is chosen so that a desired volumetric flow rate through the heat exchanger is achieved.

For temporary operation the butterfly valves are rotated through 90 so that their valve wings 46, 47 are in line with the upright diametric partition 37. Such a temporary operation position is shown in FIG. 9. The transfer compartment is not altered.

Under these conditions the heat exchanger works as a two pass arrangement with two banks of treatment tubes E and F. The inlet 11 is associated with the first bank E which includes all the tubes on the right hand side of the diametric partition 37 in FIG. 9. All the cells on that side are in communication with the inlet 11.

Thus the liquor passes down the first bank E on one side of the heat exchanger and returns from the transfer compartment 23 along the second bank F formed by the remaining tubes on the other side. The liquor returning through the second bank F comes out in the remaining control cells that are all in communication with the outlet.

If the pumping rate is maintained constant the linear flow rate of the liquor through the tubes 14 is constant. Thus with the temporary two pass arrangement approximately twice the volume of liquor can be processed in a given time. It will be appreciated that a greater thermal energy input would be required because the heat transfer area or time is about halved. However the plant can continue to run under these conditions and it is generally preferred to run in this way rather than shut down. Moreover, because the linear flow rate is retained substantially constant through the tubes the pumping apparatus can operate at substantially constant power so there is no need for reserve power in the pumping system to function during temporary operation.

In through flow fluid treatment plant a number of heat exchangers according to the invention may be employed. The heat exchangers are preferably arranged in two or more separate trains. The trains are connected in parallel so that the liquor to be treated passes through both of them and the heat exchangers in each train are preferably connected in series. Isolating valve means is coupled with the trains of heat exchangers for isolating one of the trains from the fluid flow. In this way if there are two trains of heat exchangers one of the trains may be isolated from the fluid flow leaving the remaining train in process all of the fluid flow. The isolated train may then be cleaned or otherwise attended to for maintenance purposes.

The train remaining in operation is converted so that each of the heat exchangers is switched to its temporary operating position. In this way it is able to process the same volume of liquor per unit time as was previously flowing through both trains.

It will be appreciated that additional heat will be required to compensate for the lesser amount of heat transfer area or time when the liquor is flowing through only one train. This assumes that the same heating result is desired. It will be appreciated that although the additional heat will be required it is possible to continue the plant in running order without the need to provide for excess pumping capacity to process the liquor during cleaning operations.

Various alterations, modifications and/or additions may be introduced into the foregoing construction and arrangement of parts without departing from the ambit of the invention as defined by the appended claims.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A heat exchanger including: a treatment compartment, a flow control compartment at one end of said treatment compartment, a transfer compartment at the other end of said treatment compartment, means permanently dividing said transfer compartment into a plurality of transfer cells, a fluid inlet opening into said flow control compartment, a fluid outlet leading out of said flow control compartment, a bundle of fluid treatment tubes each extending from said flow control compartment through said treatment compartment to said transfer compartment, means dividing said flow control compartment in a plurality of flow cells including adjustable flow control means independent of said inlet and outlet in said flow control compartment to directly connect a different number of said treatment tubes to said inlet and outlet respectively, said flow control and transfer compartments and said treatment tubes being arranged so that fluid entering said fluid inlet passes through said flow control and transfer compartments and back and forth through said treatment compartment via said treatment tubes in a flow pattern and out through said outlet, the number of passes the fluid makes through said treatment compartment via said treatment tubes being dependent upon the adjustment of said flow control means.

2. A heat exchanger as claimed in claim 1 wherein said flow control means has two positions of adjustment in one of which the fluid makes twice the number of passes through the treatment compartment compared with the other adjustment position.

3. A heat exchanger as claimed in claim 2 wherein the means dividing said flow control compartment is a plurality of intersecting cell partitions dividing the flow control compartment into said plurality of cells, each cell being in fluid communication with a separate group of said treatment tubes, one of said cells being in fluid communication with said fluid inlet and a separate one of said cells being in fluid communication with said fluid outlet, said flow control valve means interacting with said cell partitions.

4. A heat exchanger as claimed in claim 3 wherein said positions of adjustment provide for the fluid making four passes and two passes through said treatment compartment respectively.

5. A heat exchanger as claimed in claim 4 wherein said cell partitions comprise one diametric partition and two spaced cross partitions extending transversely of the diametric partition to form six cells, two valve apertures formed in said cell partitions, one at each of the two zones of intersection between the diametric and cross partitions, said flow control valve means including two butterfly valve assemblies each having a butterfly valve member mounted for operation in one of said valve apertures.

6. A heat exchanger as claimed in claim wherein said fluid inlet communicates with the lowest cell on one side of the diametric partition which is upright and said fluid outlet communicates with the uppermost cell on the other side of said diametric position.

7. A heat exchanger including:

a transfer compartment and a flow control compartment,

a treatment zone located between said compartments,

a bundle of fluid treatment tubes extending from the transfer compartment through said treatment zone to the flow control compartment;

means dividing said transfer compartment into a plurality of transfer chambers;

a fluid inlet opening into said flow control compartment,

a fluid outlet leading out of said flow control compartment, and adjustable flow control means independent of said inlet and outlet located in said flow control compartment;

said flow control means being adjustable so that in one position of adjustment fluid entering said inlet passes in a flow path through said flow control and transfer compartments, back-and-forth in a flow pattern through said treatment zone via said treatment tubes, and out through said outlet; and

in another position of adjustment of said flow control means fluid entering said inlet passes along said same flow path and out through said outlet but with a different back-and-forth flow pattern through said treatment zone involving a different number of passes through said treatment tubes.

8. A plurality of heat exchangers as defined in claim 7, isolating valve means interconnecting said exchangers so that they can be connected in parallel trains in normal operation and, upon operation of said valve means, connected to isolate one of said trains from the fluid flow.

9. A heat exchanger as claimed in claim 7 wherein said flow control means has two positions of adjustment in one of which the fluid makes four passes through said treatment zone and in the other of which said fluid makes two passes through said treatment zone.

10. A plurality of heat exchangers as defined in claim 9 connected in two parallel trains, each train having a plurality of said heat exchangers connected directly to each other in series, isolating valve means interconnecting said trains so that fluid flows through both of said trains in normal operation and, upon operation of said valve means, selectively isolates each of said trains from the fluid flow.

11. A heat exchanger as claimed in claim 7 wherein said flow control compartment has one diametric partition and two spaced cross partitions extending transversely of the diametric partition and dividing said flow control compartment into six cells, each cell being in fluid communication with a separate group of said treatment tubes, one of said cells being in fluid communication with said inlet and a separate one of said cells being in fluid communication with said outlet, two valve apertures formed in said cell partitions, one at each of the two zones of intersection between the diametric and cross partitions, said flow control means including two butterfly valve assemblies interacting with said cell partitions and each mounted for operation in a separate one of said valve apertures.

12. A heat exchanger as claimed in claim 11 wherein said flow control means has two positions of adjustment in one of which the fluid makes four passes through said treatment zone and in the other of which said fluid makes two passes through said treatment zone.

13. A heat exchanger as claimed in claim 12 wherein said diametric partition is upright and said inlet communicates with the lowest cell on one side of said diametric partition and said outlet communications with the uppermost cell on the other side of said diametric partition. 

1. A heat exchanger including: a treatment compartment, a flow control compartment at one end of said treatment compartment, a transfer compartment at the other end of said treatment compartment, means permanently dividing said transfer compartment into a plurality of transfer cells, a fluid inlet opening into said flow control compartment, a fluid outlet leading out of said flow control compartment, a bundle of fluid treatment tubes each extending from said flow control compartment through said treatment compartment to said transfer compartment, means dividing said flow control compartment in a plurality of flow cells including adjustable flow control means independent of said inlet and outlet in said flow control compartment to directly connect a different number of said treatment tubes to said inlet and outlet respectively, said flow control and transfer compartments and said treatment tubes being arranged so that fluid entering said fluid inlet passes through said flow control and transfer compartments and back and forth through said treatment compartment via said treatment tubes in a flow pattern and out through said outlet, the number of passes the fluid makes through said treatment compartment via said treatment tubes being dependent upon the adjustment of said flow control means.
 2. A heat exchanger as claimed in claim 1 wherein said flow control means has two positions of adjustment in one of which the fluid makes twice the number of passes through the treatment compartment compared with the other adjustment position.
 3. A heat exchanger as claimed in claim 2 wherein the means dividing said flow control compartment is a plurality of intersecting cell partitions dividing the flow control compartment into said plurality of cells, each cell being in fluid communication with a separate group of said treatment tubes, one of said cells being in fluid communication with said fluid inlet and a separate one of said cells being in fluid communication with said fluid outlet, said flow coNtrol valve means interacting with said cell partitions.
 4. A heat exchanger as claimed in claim 3 wherein said positions of adjustment provide for the fluid making four passes and two passes through said treatment compartment respectively.
 5. A heat exchanger as claimed in claim 4 wherein said cell partitions comprise one diametric partition and two spaced cross partitions extending transversely of the diametric partition to form six cells, two valve apertures formed in said cell partitions, one at each of the two zones of intersection between the diametric and cross partitions, said flow control valve means including two butterfly valve assemblies each having a butterfly valve member mounted for operation in one of said valve apertures.
 6. A heat exchanger as claimed in claim 5 wherein said fluid inlet communicates with the lowest cell on one side of the diametric partition which is upright and said fluid outlet communicates with the uppermost cell on the other side of said diametric position.
 7. A heat exchanger including: a transfer compartment and a flow control compartment, a treatment zone located between said compartments, a bundle of fluid treatment tubes extending from the transfer compartment through said treatment zone to the flow control compartment; means dividing said transfer compartment into a plurality of transfer chambers; a fluid inlet opening into said flow control compartment, a fluid outlet leading out of said flow control compartment, and adjustable flow control means independent of said inlet and outlet located in said flow control compartment; said flow control means being adjustable so that in one position of adjustment fluid entering said inlet passes in a flow path through said flow control and transfer compartments, back-and-forth in a flow pattern through said treatment zone via said treatment tubes, and out through said outlet; and in another position of adjustment of said flow control means fluid entering said inlet passes along said same flow path and out through said outlet but with a different back-and-forth flow pattern through said treatment zone involving a different number of passes through said treatment tubes.
 8. A plurality of heat exchangers as defined in claim 7, isolating valve means interconnecting said exchangers so that they can be connected in parallel trains in normal operation and, upon operation of said valve means, connected to isolate one of said trains from the fluid flow.
 9. A heat exchanger as claimed in claim 7 wherein said flow control means has two positions of adjustment in one of which the fluid makes four passes through said treatment zone and in the other of which said fluid makes two passes through said treatment zone.
 10. A plurality of heat exchangers as defined in claim 9 connected in two parallel trains, each train having a plurality of said heat exchangers connected directly to each other in series, isolating valve means interconnecting said trains so that fluid flows through both of said trains in normal operation and, upon operation of said valve means, selectively isolates each of said trains from the fluid flow.
 11. A heat exchanger as claimed in claim 7 wherein said flow control compartment has one diametric partition and two spaced cross partitions extending transversely of the diametric partition and dividing said flow control compartment into six cells, each cell being in fluid communication with a separate group of said treatment tubes, one of said cells being in fluid communication with said inlet and a separate one of said cells being in fluid communication with said outlet, two valve apertures formed in said cell partitions, one at each of the two zones of intersection between the diametric and cross partitions, said flow control means including two butterfly valve assemblies interacting with said cell partitions and each mounted for operation in a separate one of said valve apertures.
 12. A heat exchanger as claimed in claim 11 wherein said flow cOntrol means has two positions of adjustment in one of which the fluid makes four passes through said treatment zone and in the other of which said fluid makes two passes through said treatment zone.
 13. A heat exchanger as claimed in claim 12 wherein said diametric partition is upright and said inlet communicates with the lowest cell on one side of said diametric partition and said outlet communications with the uppermost cell on the other side of said diametric partition. 